1. Field of the Invention
The present invention relates to an electrode material and an electrode of a p-type Group III-V compound semiconductor used for an ultraviolet light- or blue light-emitting diode, a laser diode or the like. More particularly, it relates to an electrode material and an electrode, capable of obtaining an ohmic contact.
2. Description of the Related Art
As a material of light-emitting devices such as ultraviolet light- or blue light-emitting diode, laser diode or the like, a nitride compound semiconductor represented by the general formula In.sub.x Ga.sub.y Al.sub.z N (provided that x+y+z=1, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, and 0.ltoreq.z.ltoreq.1) has been known. Electrodes having good current injection characteristics for bringing into contact with either p-type or n-type layers are essential for producing the light-emitting device.
As an electrode material for n-type compound semiconductor, Al and a Ti--Al alloy have hitherto been known as a good electrode material.
As an electrode material for p-type Group III-V compound semiconductor, Au, a Ni--Au alloy, a Mg--Au alloy and a Zn--Au alloy have been known. However, a contact resistance is larger than that of the electrode material for n-type Group III-V compound semiconductor, which leads to a factor of increasing a driving voltage of a light-emitting device. Particularly, in a semiconductor laser into which a large current is injected, there was a problem that the driving voltage becomes very larger because of a large contact resistance.